This invention relates to an image-receiving element for use in photographic and photothermographic film units of the diffusion transfer type. More particularly, the invention relates to an image-receiving element especially adapted for use in diffusion transfer film units of the type wherein an image-receiving element is designed to be separated from a photosensitive element after exposure and processing.
Photographic film units for use in diffusion transfer type photographic processes are well known. Such film units including both "peel apart" (i.e. wherein an image-receiving element is separated from a photosensitive element after exposure and processing) and "integral" (wherein the image-receiving element and photosensitive element are maintained as a superimposed integral unit after exposure and processing) formats. Various embodiments of "peel apart" and "integral" formats are known in the art including those wherein images are formed in black and white, and color, as described in: E. H. Land, H. G. Rogers, and V. K. Walworth, in J. M. Sturge, ed., Neblette's Handbook of Photography and Reprography, 7th ed., Van Nostrand Reinhold, N.Y., 1977, pp. 258-330; and V. K. Walworth and S. H. Mervis, in J. Sturge, V. Walworth, and A. Shepp, eds., Imaging Processes and Materials: Neblette's Eighth Edition, Van Nostrand Reinhold, N.Y., 1989, pp. 181-225. Additional examples of "peel apart" film units are described in U.S. Pat. Nos. 2,983,606; 3,345,163; 3,362,819; 3,594,164; and 3,594,165.
In general, diffusion transfer photographic products and processes involve film units having a photosensitive element including at least one silver halide layer. After photoexposure, the photosensitive element is developed, generally by uniformly distributing an aqueous alkaline processing composition over the photoexposed element, to establish an imagewise distribution of a diffusible image-providing material. The image-providing material, (typically image dyes or complexed silver), is selectively transferred, at least in part, by diffusion to an image-receiving layer or element positioned in a superposed relationship with the developed photosensitive element and capable of mordanting or otherwise fixing the image-providing material. The image-receiving layer retains the transferred image for viewing. In diffusion transfer photographic products of the "peel-apart" format, the image is viewed in the image-receiving layer upon separation of the image-receiving element from the photosensitive element after a suitable imbibition period. With "integral" formats, such separation is not required.
Black and white transfer images are generally formed by exposing and developing a silver halide emulsion, and subsequently dissolving and transferring silver from unexposed, or less exposed regions, to an image-receiving layer containing silver precipitating agents or nuclei. Color images are generally formed by the imagewise transfer of image dyes from a photosensitive element to an image-receiving layer containing a dye mordant material.
Image-receiving elements particularly adapted for use in "peel-apart" diffusion transfer film units usually include an image-receiving layer for retaining the transferred image. This image-receiving layer is typically arranged on a substrate layer of suitable material or a combination of layers arranged on the substrate layer, each of the layers providing specific and desired functions adapted to the formation of the desired image in accordance with diffusion transfer processing. In one well known photographic embodiment, the image-receiving element comprises a support material (preferably, an opaque support material carrying a light-reflecting layer for the viewing of the desired transfer image thereagainst by reflection); a polymeric acid-reacting (neutralizing) layer adapted to lower the environmental pH of the film unit subsequent to substantial transfer image formation; a spacer or timing layer adapted to slow the diffusion of the alkali of an aqueous alkaline processing composition toward the polymeric neutralizing layer; and an image-receiving layer to receive the transferred photographic image. Such a structure is described, for example, in the aforementioned U.S. Pat. No. 3,362,819 and is illustrated in other patents, including U.S. Pat. Nos. 4,322,489 and 4,547,451.
Photothermographic film products for use in diffusion transfer type processes are also well known in the art. Various embodiments of such film products are known and typically comprise: 1) a photosensitive element including at least one photosensitive silver halide emulsion and a corresponding image providing material (e.g. silver for black and white embodiments, image dyes for color embodiments), and 2) an image-receiving element including an image receiving layer. Typically, the photosensitive element is exposed and subsequently brought in superposed contact with the image-receiving element, wherein the assembly is heated for a predetermined time period. In addition to heating, some applications require a small amount of water to be added to the photosensitive element prior to lamination with the image-receiving element. The application of heat, (and water if used), results in the image-wise diffusion of image materials from the photosensitive element, to the image-receiving element. Subsequently, the image-receiving element is separated from the photosensitive element. Various embodiments of photothermographic film units and processes are described in: S. H. Mervis and V. K. Walworth, Kirk-Othmer Encyclopedia of Chemical Technology, 4th. Edition, Volume 6, John Wiley & Sons, Inc. 1993, pp. 1036-1039. Specific examples of such film units are described in U.S. Pat. Nos. 4,631,251; 4,650,748; 4,656,124; 4,704,345; 4,975,361; and 5,223,387.
The surface of the image-receiving elements used in "peel apart" photographic and photothermographic film products is often susceptible to tackiness due to the absorption of moisture. Moisture may be provided by the environment, or by way of the processing conditions, which may include the introduction of water and/or other processing liquid. As a result of the absorption of moisture, the surface of the image-receiving element may become wet and sticky. As such, image-receiving elements often cannot be stacked upon one another during storage and/or manufacturing without blocking, i.e. sticking between individual elements.
Furthermore, in photographic embodiments, the surface of the image-receiving element often remains wet and sticky for some period of time after it has been separated from the photosensitive element. During this time period care must be exercised in the handling of the photograph so as not to damage it. Further, in instances where it is desired to place the photograph in a holder of some type for storage purposes, or where it is desired to laminate a protective layer over the photograph, it is necessary to wait until the surface of the photograph is sufficiently dry to permit it to be handled in that manner. The time period required to allow such handling varies dependent upon various factors such as the amount of liquid taken up by the image-receiving layer during photographic processing and the ambient relative humidity and temperature conditions. Additionally at any time after processing and drying, the photograph may encounter humid conditions which can render the surface of the photograph wet and sticky.
Thus, it is desired to provide an image-receiving element which maintains a relatively non-stick, substantially dry outer surface under humid environmental conditions. Furthermore, with photographic film units, it is desired to reduce the time period following photographic processing before which the image-receiving element can be further handled.